Search for Cosmic Ray Anisotropy with the Alpha Magnetic Spectrometer on the International Space Station

TL;DR

This study uses five years of AMS data to search for cosmic ray anisotropy, finding no significant anisotropy or seasonal variations across various particle types and energy ranges.

Contribution

It provides new upper limits on cosmic ray anisotropy for positrons, electrons, and protons at high energies, based on extensive AMS observations.

Findings

Positron to electron ratio is isotropic at all energies.

Upper limits on dipole anisotropy are set for positrons, electrons, and protons.

No seasonal excess observed in cosmic ray fluxes.

Abstract

The search for cosmic ray anisotropy has been performed using particles collected by the Alpha Magnetic Spectrometer after the first five years of operation. The positron to electron ratio is consistent with isotropy at all energies and angular scales. The limit on the dipole anisotropy at the 95% confidence level for energies above 16GeV is $\delta<0.020$ for positrons and $\delta<0.006$ for electrons. In the case of high rigidity protons the upper limit in the rigidity range from 80 to 1800GV is $\delta<0.003$. No indication of seasonal excess is observed for all particle species within the present statistics.